1. Field of the Invention
The present invention is generally concerned with switches of the type usually employed to control the supply of electrical power to a circuit of any kind.
2. Description of the Prior Art
Generally speaking, a switch of this kind comprises a set of parts usually referred to as the mechanism and which constitute its active part inside a housing and controlled by an operating member such as a pivoting toggle or a pushbutton, for example, accessible to the user operating the switch.
The present invention is more particularly directed to the case where a mechanism of this kind comprises, movably mounted between a fixed yoke and at least one fixed contact, at least one conductive contact arm which is articulated to the fixed yoke, which is itself conductive, and which is controlled by the associated operating member to assume one or other of two positions in one of which it bears against the fixed contact, through a bearing area, and in the other of which it is spaced from the latter either because, in the case of a single-throw switch, it is not then bearing against any other fixed contact or bears against a "rest", or because, in the case of a double-throw switch, it bears against another fixed contact in this second position.
One problem in manufacturing switch mechanisms of this type concerns the articulation to be obtained between the conductive contact arm and the fixed yoke given that, over and above its pivoting function, this articulation also has to transmit current.
At present this articulation is achieved by means of a single pivot.
In practice the fixed yoke usually comprises to this end a pivoting area and the conductive contact arm itself comprises, for cooperating with this pivoting area, by means of a knife-edge articulation, for example, an area which will be referred to hereinafter for convenience only as the contact area, this area normally remaining in permanent contact with the pivoting area of the fixed yoke.
In fact it appears that in operation, that is to say during actuation of the mechanism, unwanted rebounds occur in the articulation between the contact area of the conductive contact arm and the pivoting area of the fixed yoke.
Each rebound in practice results in arcing between the contact area of the conductive contact arm and the pivoting area of the fixed yoke, which leads to gradual deterioration of the conductive contact arm and/or the fixed yoke to the detriment of the required transmission of current.
The conductive contact arm is subject to progressive oxidation of its surface, for example, and where it is made from brass it is also subject to structural changes due to migration of zinc towards its surface.
As the conditions under which current is transmitted are then modified, there inevitably results unwanted overheating between the conductive contact arm and the fixed yoke which, independently of any deleterious effect on the mechanical strength of the surrounding insulative material, can only accentuate the deterioration of which it is a sign.
An attempt is usually made to remedy this disadvantage by applying grease to the articulation area concerned, but this remedy is inadequate.
A general objective of the present invention is an arrangement providing a simple and effective way to overcome this difficulty which also yields other advantages.